Scroll to navigation

UMASK(2) System Calls Manual UMASK(2)

NAME

umask —
set file creation mode mask

LIBRARY

Standard C Library (libc, -lc)

SYNOPSIS

#include <sys/stat.h>

mode_t
umask(mode_t numask);

DESCRIPTION

The umask() routine sets the process's file mode creation mask to numask and returns the previous value of the mask. The 9 low-order access permission bits of numask are used by system calls, including open(2), mkdir(2), and mkfifo(2), to turn off corresponding bits requested in file mode. (See chmod(2)). This clearing allows each user to restrict the default access to his files.

The default mask value is S_IWGRP|S_IWOTH (022, write access for the owner only). Child processes inherit the mask of the calling process.

RETURN VALUES

The previous value of the file mode mask is returned by the call.

ERRORS

The umask() system call is always successful.

SEE ALSO

chmod(2), mkfifo(2), mknod(2), open(2)

STANDARDS

The umask() system call is expected to conform to IEEE Std 1003.1-1990 (“POSIX.1”).

HISTORY

The umask() function appeared in Version 7 AT&T UNIX.
June 4, 1993 Linux 4.9.0-9-amd64